Theorem bj-aecomsv

Description: Version of aecoms with a disjoint variable condition, provable from Tarski's FOL. The corresponding version of naecoms should not be very useful since -. A. x x = y , DV ( x , y ) is true when the universe has at least two objects (see dtru ). (Contributed by BJ, 31-May-2019) (Proof modification is discouraged.)

	Ref	Expression
Hypothesis	bj-aecomsv.1	|- ( A. x x = y -> ph )
Assertion	bj-aecomsv	|- ( A. y y = x -> ph )

Proof

Step	Hyp	Ref	Expression
1		bj-aecomsv.1	|- ( A. x x = y -> ph )
2		aevlem	|- ( A. y y = x -> A. x x = y )
3	2 1	syl	|- ( A. y y = x -> ph )